Sansui 9090 (not DB) only some function lights working

[MBuras]

EDIT: FIXED

Was wrapping up a quick tuneup which has now become a long drawn out headache. The function lights for only phono and aux do not illuminate. Replaced bulbs with no effect. Checked power, fuses, etc. The 6.5vac power is present at pin 39, and is transferred to the function bulbs for both FM modes and AM.

Reading up on other users having problems with the wafer switches I went ahead and pulled the switch assembly. Disassembled to work on each wafer individually. Multiple coats of D5 as well as a burnishing tool to get rid of all the deposits. All back together and same problem exists.

Been looking for cracks, poking and prodding, ohming out the power in to function pins. On the FM and AM modes everything gets a tone as expected. On phono and aux I can only get a tone if I rock the switch slightly to land between the detents. And even then no every time. But I'm watching the wafers as I do this and still can't see where the disconnect is. Pulling out what little hair I have left on this. Please help.

 

[avionic]

On the FM and AM modes everything gets a tone as expected. On phono and aux I can only get a tone if I rock the switch slightly to land between the detents.

Dirty switch or cold solder connection.

 

[tutor_turtle]

It's been a while since I did my last 9090. Remind me, does this have the cartridge style lamps?
If so, I just did a service on a 771, the complaint was noise/flicking dash lamps.
The clips that hold the lamp ends had all cold fractured, I mean every single joint had to be reflowed.
If the lamp voltage is getting through the wafer, the open connection has to be on the terminus end.

 

[MBuras]

Dirty switch or cold solder connection.

That was my assessment as well but nothing I clean with seems to be improving the situation. I did reflow all those pins just in case.

If the lamp voltage is getting through the wafer, the open connection has to be on the terminus end.

The voltage isn't making it through the wafer for aux and phono.

This is going to sound silly but it's almost like the contact on the front wafer is a little short. The times I can make the connection between phono or aux and the power supply tones out is when I can move the wafer just enough to make contact with both points. But in it's detented position it misses the power connection.

In this photo (front is removed) you can see where the wafer lands for aux. The red circle on the right is the aux. The red circle on the left is the 6.5vac supply. And no joy on the ohm tone.


But here when I catch both part of the aux (right) and the edge of the power supply (left) I get tone. But of course that doesn't work for a detended switch.


Same with the phono. It missed the other edge of that metal plate by a mm or two.

I'm really not understanding something here. Appreciate all the suggestions. Thx

 

[kwayde]

That was my assessment as well but nothing I clean with seems to be improving the situation. I did reflow all those pins just in case.

The voltage isn't making it through the wafer for aux and phono.

This is going to sound silly but it's almost like the contact on the front wafer is a little short. The times I can make the connection between phono or aux and the power supply tones out is when I can move the wafer just enough to make contact with both points. But in it's detented position it misses the power connection.

In this photo (front is removed) you can see where the wafer lands for aux. The red circle on the right is the aux. The red circle on the left is the 6.5vac supply. And no joy on the ohm tone.
View attachment 3138065

But here when I catch both part of the aux (right) and the edge of the power supply (left) I get tone. But of course that doesn't work for a detended switch.
View attachment 3138067

Same with the phono. It missed the other edge of that metal plate by a mm or two.

I'm really not understanding something here. Appreciate all the suggestions. Thx

Are you sure about where the power comes in? The large tab on the disk that is just contacting where you say the 6.5v comes in isn't wide enough for it to work on the five function tabs. It is only four tabs wide.

I think the 6.5 volts comes in at the tab next to Aux. It contacts the disc no matter where the switch is positioned.
The contact tabs for Aux and phono may just need to be bent in a bit to make good contact.

Here's your pic revised, then one of my pics from one I repaired.

 

[MBuras]

I tried putting a little extra bend in that contact you mentioned and got continuity through all the functions while the switch was on my desk. But reinstalled I still have the same old issue.

I'm afraid to open it up for a 4th time but cleaning is almost all that makes sense at this point. It is pretty crusty on the inside like it had been sitting in a basement for a while so maybe just needs the cleaner to soak in and cut through all the yuck.

Thanks for the ideas.

 

[tutor_turtle]

These folks part-out vintage hifi.
They list every single part, scroll down, find your model and start looking.
It's a long list.

Vintage Sansui stereo parts & spares

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If they don't have your switch, no one does.

Good luck.

 

[MBuras]

Many thanks for the participation on this thread. It was exactly what I needed to move forward. Issue fixed.

So there was some confusion on my part back a few posts because I said the power was coming in on pin 39 but @kwayde asked if I was sure and said it should be coming in on 41 (that's where the trace goes from the pin pictured). Then I noticed (should've noticed it sooner - duh) that all my lights were on all the time. But this shouldn't be possible without the pin mod on the top side of the board (essentially moving the red wire from 39 to 41 within the connector). I hadn't done the mod and confirmed it still wasn't done.

After finding a bottom side picture of F-2541 on Ebay I confirmed that my power wire had be moved at some point from 41 to 39 on the bottom of the board. Someone's attempt at the lighting mod but unfortunately it doesn't work that way. On the trace side I move the power wire back from 39 to 41 and bingo everything works as expected including no dial lights for aux or phono as designed. I did the quick pin mod to get the lights on all the time, moving the pin in the connector this time, and yep, everything works like the mod should.

As found so didn't know it was wrong


Fixed and back in it's intended position


A little long winded but thought this might be helpful for someone in the future. Only move the connector pin on top of the board to change the lighting to constant. Moving the supply wire underneath will only cause issues. And never trust that what you're looking at is factory work.

 

[JosieDog2]

Help! My Sansui 9090 has a selector function problem. Power meters, signal/tuner meter and dial face lights all work. Red wire mod had already been done by someone else. My issue is when selector switch goes to phono, Dolby fm, am, or aux there is no light for that function on the dial face plate. Deoxit the switch, tried to re-bend switch contact tab, re-flowed every solder joint I could find on the light box board. something that may be telling is fm stereo light works, but is weak. Function lamps are all good when tested Individually. I think the illumination box board is getting power, thus the fm stereo light is working, but somewhat faint. I am out of ideas!!!!! Any thoughts. Thanks for your responses. Take the switch apart???

 

[JosieDog2]

Are the function tabs on the first wafer supposed to contact the wheel on top of the wheel or under It?

 

[Young46]

Are the function tabs on the first wafer supposed to contact the wheel on top of the wheel or under It?

Just a suggestion but you will probably have better luck getting help by starting a new (your own) thread.